1. Field of the Invention
This invention relates to a new mechanism which, by enabling the selection command for varying the reed beating position in a terry loom to be effectively transmitted, allows the reed positions to be precisely stabilized, to hence form terries which are perfectly equal over the entire length of the terry cloth, hence obtaining terry cloth of optimum quality.
2. Background of the Discussion
More specifically, the invention relates substantially to an improvement in the device already described in our preceding U.S. Pat. No. 4,406,308 granted on Sep. 27, 1983.
As is well known, in terry looms the reed, swinging with the loom sley, must always be moved either into a normal or "closed" position in which said reed beats the inserted weft yarns against the edge of the cloth under formation, or into a position retracted from said edge or "open" position in which the inserted weft yarns are carried by the reed only into the vicinity of said edge but without them being beaten against it.
In other words, the reed beating position has to be able to be varied relative to the edge of the cloth under formation by means of a suitable device, such that the reed effects the actual beating only after a number of yarn insertions, to hence create the characteristic terry of the terry cloth.
In a device for varying the reed beating position in a terry loom, such as that described in the said U.S. Pat. No. 4,406,308, the reed is hinged to the loom sley and has its lower end connected by connecting rods to cams keyed onto a single shaft which, via a gearwheel rigid with it, engages a toothed sector supported by a body mounted so as to be idle about the axis of rotation of said sley and is hinged to the lower end of said sley by two arms pivoted to each other at a common articulated joint. Said toothed sector is then rotated relative to said cams by a rocker lever which, pivoted to a fixed part of the loom and maintained resting by means of a spring against a fixed shoulder of the loom, at which the reed is in said "closed" position, is in its turn rotated into a second position, corresponding to the reed in its "open" position, by a device which selects the movement of the rocker lever by a mechanism for transmitting the selection command.
More specifically, said selection command transmitting mechanism consists substantially of a groove provided at the end of said rocker lever, into which said common articulated joint of the two said pivoted arms is inserted and guided, said groove having a circular arc extension with its center on said axis of rotation of the sley when said rocker lever is resting against said fixed shoulder.
Although such transmission mechanism has considerable kinematic advantages an important one of which is the assurance that the reed is always specifically in its "closed" position when the sley swings into its rear dead center position, this being known to be essential in order not to have interference between the reed and the heddle frames, with consequent damage to the heddles, it has however certain drawbacks due substantially to the type of joint-groove connection used.
In this respect, in said type of connection there must always be a clearance between the joint and the groove to enable them to slide relative to each other, this inevitably resulting in imperfect and non-constant positioning of the reed in the commanded position, consequently obtaining terry cloth having an irregular terry height. Again, said clearance is also the source of an uncontrollable series of impacts and sliding of said joint against the walls of said groove under the action of the alternating loads generated during operation, consequently prejudicing the life of the connection.